The present invention relates to devices such as surface acoustic wave (SAW) devices which constitute, for example, surface acoustic wave filters or surface acoustic wave resonators, and devices which handle high frequency signals, and more particularly to a small high-performance high-frequency module suitable for use in a radio communication device such as a portable telephone set.
One example of the conventional packaged surface acoustic wave modules is shown in FIG. 2a. A surface acoustic wave device 2 is die-bonded within a metal package 3, hermetically sealable with a bond 4, and connected to package terminals 12 by wire bonding at 16 through bonding pads 11.
FIGS. 2b, 2c and 2d show hypothetical examples of a structure including a surface acoustic wave device package shown in FIG. 2a die-bonded to a mother board, for example, of a communication device. Generally, the impedance viewed from the input/output terminals 12 of the surface acoustic wave device is capacitative on the order of several pF because of the existence of capacitance involving the finger electrodes of a transducer 1 (FIG. 2a) which excites surface acoustic waves. Therefore, as shown in FIG. 2b, after a surface acoustic wave device package 3 is die-bonded to a mother board 17, for example, of a communication device terminal, external inductive matching circuits 18a, 18b are connected to the input/output terminals to cancel the capacitance components, as shown in FIG. 2c, 2d. Reference numeral 120 denotes input/output lines (FIGS. 2b, 2c, 2d) and 130. (FIG. 2d) denotes a ground potential layer at which a surface to which the package 3 and high frequency device 2 are attached is maintained via through holes 131 (FIG. 2d). FIG. 2d shows the opposite side of the mother board from the package 3 of FIG. 2b.
Such conventional SAW device shown in FIG. 2a is disclosed, for example, in "800-MHz HIGH-PERFORMANCE SAW FILTER USING NEW RESONANT CONFIGURATION", IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-33, No. 6, June 1985, pp. 510-518, and "Miniature SAW Antenna Duplexer for 800-MHz Portable Telephone Used in Cellular Radio Systems", IEEE Transactions on Microwave Theory and Techniques, Vol. 36, No. 6, June 1988, pp. 1047-1056.